In most oil reservoirs, when their natural energy is not enough for extracting oil efficiently, either the tertiary or secondary recovery processes are used to increase the production. Currently, around 70% of the world oil production comes from fields that are more than 30 years old, which has drawn the attention of the industry to mature fields (also known as marginal fields) whose production is declining. Mature fields are found all over the world.
In the Gulf of Mexico continental plate there is a number of mature fields that are in advanced stages of their productive lives. In water-wettable-sand reservoirs, which contain intermediate oil and are at a decaying oil production stage, the use of the secondary recovery by water presents potential risks such as early water irruption in the production well.
Part of the oil that is found in the pores is residual oil, but a large amount of oil is located at zones that are neither connected nor swept by water, which makes the production wells yield a high percentage of water. In this case, the application of polymers or alkalis hardly increases the production rate because these compounds are dragged along with the water flow in the production well.
Occasionally, the injection of mixtures of such additives (ASP) can work well, but they are very selective and sometimes the extraction does not achieve a good recovery factor; in other cases, the gel or foam application program is used to control water, which represents normally a high production cost. Currently, the world trend for diminishing the water production in oil fields is based on the following methods: application of triblock polymers, in-situ generation of polymeric gels [SPE 94660 K. Elewaut et al.], injection of oil-type emulsions in water stabilized with surfactants [SPE 152290 M. L. Rocha de Farias et al.], and injection of silicon-based emulsions for rock hydrophobization.
The last method, which was used successfully in the Algyö oil fields in Hungary [I. Lakatos et al. SPE 78307; I. Lakatos et al. SPE 80204; I. Lakatos et al. SPE 112403], and in the Yuzhno-Balykskoye and Romanshkinsky fields in Russia [Burger et al. Process for the extraction of crude oil. U.S. Pat. No. 5,630,474 (1997); G. B. Fridman et al. A004 12th European Symposium on Improved Oil Recovery—Kazan, Russia, 8-10 Sep. 2003], is based on different mechanisms: 1) alteration of the rock wettability to be oil wettable, modifying the capillary forces; 2) zone partial blockage by plugging the rock pores by the emulsion disperse phase; and 3) modification of the relative permeability, which provokes the reduction of water mobility [V. R. Guillen et al. Transport in Porous Media, V. 86(2) 2011; V. R. Guillen et al. International Journal of Multiphase Flow, 2012; L. Romero et al. SPE/DOE 35461; S. Cobos et al. International Journal of Multiphase Flow 35 (2009) 507-515; K. Taylor ACS 1992; M. I. Romero et al. Physical Review. E 84, 046305 (2011)].
The injection of water with the aqueous emulsion batch could be an option for the recovery of oil in sandstone fields flooded with water or that contain oil with approximately 20° API gravity, where the application of ASP technologies, injection of polymers, gels or foams can represent technological problems or high costs.
U.S. Pat. No. 4,197,912 discloses an oil extraction process using a mixture of organic silicon compounds dispersed or dissolved in hydrocarbons. However, the amount and concentration of the chemical compounds do not make this process financially feasible. U.S. Pat. No. 4,074,536 discloses a rock hydrophobization process using organic silicon compounds, which form a thin layer on the rock surface and work as water repellents. U.S. Pat. Nos. 4,296,812 and 4,230,182 disclose similar oil recovery processes by means of emulsions, where the continuous phase is the surfactant aqueous solution and the dispersed phase contains 15% dialkylsiloxane hydrocarbons.
U.S. Pat. No. 6,165,948 and the paper by Chunyan Feng et al. [Chunyan Feng, Ying Kong, Guancheng Jiang, Jinrong Yang, Chunsheng Pu, Yuzhong Zhang, Wettability modification of rock cores by fluorinated copolymer emulsion for the enhancement of gas and oil recovery, Applied Surface Science 258 (2012) 7075-7081] refer to a rock hydrophobization method by using hydrophobic substances such as silicon-based waxes, polyethylene or fluorinated compounds. Jeirani et al. [Z Jeirani, B. Mohamed Jan, B. Si Ali, I. M. Noor, C. H. See, W. Saphanuchart, Formulation, optimization and application of triglyceride microemulsion in enhanced oil recovery, Industrial Crops and Products 43 (2013) 6-14], disclose the application of triglyceride-based microemulsions for the tertiary recovery of oil. In addition, the researchers at the Alberta Petroleum Institute, Rao et al. [D. N. Rao, M. Girard, S. G. Sayegh, The influence of reservoir wettability on waterflood and miscible flood performance. PETSOC 92-06-05, 31 (1992) 47-55] concluded from the performed studies that the oil recovery by water injection is more efficient in mixed wettability systems. In the SPE 130994 paper [Q. Di, C. Shen, Z Wang, B. Jing, C. Gu, Y. Qian, Innovative Drag Reduction of Flow in Rock SPE 130994 (2010)], the authors studied the rock hydrophobization process to reduce the dragging flow rate (water), enhancing the oil extraction process.
There are diverse publications related to the application of emulsions based on either oil itself or its fractions and an emulsifier for oil recovering, for example, Ajay et al. in the paper published in Ind. Eng. Chem. Res. 2010, 49, 12756-12761 reported additional oil recovery up to 23% using an O/W-type emulsion with cog-wheel oil. On the other hand, V. C. Santana et al. featured in the Journal of Petroleum Science and Engineering 66 (2009) 117-120 a successful oil recovery test in a sand package by using an oil microemulsion. McAuliffe, at the 1972 Symposium in Tulsa, presented a research work (SPE 4369, SPE 4370) based on the development and application of the oil emulsion injection method (at 14% concentration) for tertiary recovery in the Midway-Sunset oil field in the United States. Nevertheless, in the literature, no injection method of emulsions free of siloxanes, fluorinated compounds or polymers for rock hydrophobization for additional oil recovery has been described so far.